Optical device

ABSTRACT

An optical device and a method of manufacturing an optical device. The optical device includes: a conversion means for converting propagation light propagating through an optical waveguide into parallel light and for outputting the parallel light; and a first lens means for focusing the parallel light outputted from the conversion means on a core of an optical fiber. The method includes: converting propagation light propagating through an optical waveguide into parallel light; outputting the parallel light; and focusing, using a first lens, the parallel light on a core of an optical fiber.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical communication technology,and more specifically, to an optical device in which an opticalwaveguide and an optical fiber are optically coupled.

2. Description of Related Art

In optical communication, an optical signal in a silicon opticalwaveguide is required to optically couple to an optical cable on theoutside of the waveguide. A grating (diffraction grating) structurecreated inside the slab structure of the silicon optical waveguide isoften used to focus and couple the propagating light onto the core of anoptical fiber. A schematic view of this type of optical device is shownin FIG. 1.

FIG. 1 (a) is a cross-sectional side view of the optical device 10, andFIG. 1 (b) is a plane view from below. In the optical device 10, anoxide layer (silicon oxide, silicon oxynitride or silicon nitride) 12 isprovided on a silicon substrate 11, and a silicon optical waveguide 13is formed on the oxide layer 12. A grating coupler 14 is also formed atone end of the silicon optical waveguide 13. In the grating coupler 14,a plurality of approximately concentric circular grooves are provided inparallel. An optical beam focused by the grating coupler 14 is alignedonto the core 15 of an optical fiber 16, and optical coupling isperformed between the silicon optical waveguide 13 and the optical fiber16.

In JP2002-357737A, an optical fiber guiding portion is formed in onesurface of a glass substrate so as to optically couple an optical fiberwith the glass substrate. A lens, the center of which is aligned withthat of the optical fiber guiding portion, is formed on the othersurface of the glass substrate, and the light passing through the glasssubstrate is focused by the lens onto the core of the optical fiber.

In JP05-241044A, an optical waveguide is cut so that an inclined surfaceis formed at the deflection point of the optical waveguide with respectto the surface of the substrate on which the optical waveguide has beenformed. Light is reflected by the inclined end surface. A lens is formedon the optical waveguide in the vicinity of the inclined end surface,and the light reflected by the inclined end surface is focused by thelens and directed towards an optical element.

BRIEF SUMMARY OF THE INVENTION

The present invention provides an optical device including: a conversionmeans for converting propagation light propagating through an opticalwaveguide into parallel light and for outputting the parallel light; anda first lens means for focusing the parallel light outputted from theconversion means on a core of an optical fiber.

Another aspect of the present invention provides a method formanufacturing an optical device comprising: converting propagation lightpropagating through an optical waveguide into parallel light; outputtingthe parallel light; and focusing, using a first lens, the parallel lighton a core of an optical fiber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically illustrating an optical device in theprior art for optically coupling an optical waveguide and an opticalfiber.

FIG. 2 is a diagram schematically illustrating an optical device foroptically coupling an optical waveguide and an optical fiber in a firstembodiment of the present invention.

FIG. 3 is a partial cross-sectional view of the V-shaped groovesprovided in the grating means of the optical device shown in FIG. 2.

FIG. 4 is a diagram schematically illustrating the optical device foroptically coupling an optical waveguide and an optical fiber accordingto an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In a structure, as in optical device 10, in which an optical beam isfocused by a grating coupler 14 and the focused light is directlyaligned with the core 15 of the optical fiber 16, the optical fiber hasto be aligned very precisely at the accuracy of one micrometer or lessin order to achieve high optical coupling efficiency. It is an object ofthe present invention to realize optical coupling of an opticalwaveguide and an optical fiber without requiring direct alignment of theoptical fiber with a high degree of precision. The object of the presentinvention includes providing an optical device that realizes opticalcoupling of an optical waveguide and an optical fiber in this way.

One embodiment of the optical device provided by the present inventionincludes a conversion means for converting propagation light propagatingthrough an optical waveguide into parallel light and for outputting theparallel light in a space, and a lens means for focusing the parallellight in a space outputted from the conversion means onto the core of anoptical fiber.

Preferably, according to an embodiment of the present invention, theconversion means includes a grating means (an optical diffraction meansusing an optical diffraction grating), in which the propagation light isbent at a right angle to become parallel light.

Preferably, according to an embodiment of the present invention, thegrating means is a reflective surface provided with a plurality ofV-shaped grooves arranged in parallel, in which the surface on one sideof each V-shaped groove forms a 45-degree incline.

Preferably, according to an embodiment of the present invention, theconversion means includes a reflecting means forming a 45-degree inclinefor reflecting the propagation light, and another lens means, having afocal point at the point on which propagation light is reflected by thereflecting means, that converts the light reflected by the reflectingmeans into parallel light.

Preferably, according to embodiments of the present invention, the lensmeans has a convex lens surface on the parallel light side, and a recessfor accommodating the optical fiber on the optical fiber side, therecess being formed so the parallel light is focused on the core of theoptical fiber.

Preferably, the optical waveguide is a silicon thin-film waveguide.

The present invention realizes optical coupling of an optical waveguideand an optical fiber without requiring direct alignment of the opticalfiber with a high degree of precision. The optical fiber does not haveto be aligned with high precision of one micrometer or less. Instead,this precision can be relaxed to ten micrometers or more while stillachieving high optical coupling efficiency.

The following is an explanation of a preferred embodiment of the presentinvention with reference to the drawings. However, this embodiment doesnot limit the present invention as described in the scope of the claims,and all combinations of characteristics explained in the embodiment arenot necessarily required in the technical solution of the presentinvention. The present invention can be embodied in many different ways,and is by no means limited to the content of the embodiment describedbelow. In the entire explanation of the embodiment, identicalconstituent parts and constituent elements are denoted by the samenumbers.

FIG. 2 is a diagram schematically illustrating an optical device 20 foroptically coupling an optical waveguide and an optical fiber in a firstembodiment of the present invention. FIG. 2 (a) is a cross-sectionalside view of the optical device 20, and FIG. 2 (b) is a plane view frombelow.

In this optical device 20, an oxide layer 12 is provided on a siliconsubstrate 11, and a silicon optical waveguide 13 is formed on the oxidelayer 12. However, in this optical device 20 a grating means 21 isformed on one end of the silicon optical waveguide 13 as a conversionmeans for converting light propagating through the silicon opticalwaveguide 13 to parallel light and for outputting the parallel light.

The grating means 21 spreads the light propagated therein after passingthrough the silicon optical waveguide 13, and converts the light into aparallel optical beam of parallel light outputted towards the siliconsubstrate 11. The parallel light passes through the silicon substrate11, and is outputted from the silicon substrate 11 upwards where thereis an optical fiber 16.

FIG. 3 is a partial cross-sectional view of the V-shaped groovesprovided in the grating means 21 as the diffraction grating structure.As in the case of the grating coupler 14 in FIG. 1, a plurality ofconcentric circular V-shaped grooves are provided in parallel. In orderto improve the diffraction efficiency and directionality of the light,the fine surface 31 on one side of each V-shaped groove has a roughly45-degree incline with respect to the substrate surface 21, and the finesurface 32 on the other side is formed so as to be as perpendicular aspossible. A metal film 33 of gold, silver or aluminum is formed on thefine surface 31 to make it a reflective surface.

Returning to FIG. 2, the parallel light outputted from the siliconsubstrate 11 strikes the convex lens surface 23 of the lens 22 providedas a lens means for focusing the parallel light on the core 15 of theoptical fiber 16. The convex lens surface 23 which the parallel lightstrikes is formed to focus the parallel light on a focal point insidethe lens 22.

A recess 24 for accommodating the optical fiber 16 is formed on the sideof the lens 22 opposite the convex lens surface 23. The recess 24 isformed in the center so the parallel light focused inside the lens 22 isdirected at the focal point. The core 15 of the optical fiber 16 ispositioned in the center of the recess 24. Therefore, the optical fiber16 becomes aligned when the optical fiber is placed inside the recess24.

Unlike the optical device 10 in FIG. 1, which has a structure thatfocuses the light using a grating coupler 14 and directly aligns thefocused light with the core 15 of the optical fiber 16, the opticaldevice 20 in FIG. 2, which has a structure that converts light intoparallel light using a grating means 21 and aligns the parallel lightwith the core 15 of the optical fiber 16 via a lens 22, does not requiredirect alignment of the optical fiber with a high degree of precision.Because the convex lens surface 23 and the recess 24 of the lens 22 canbe manufactured with a high degree of precision, using a moldingprocess, the optical device 20 achieves high optical couplingefficiency.

FIG. 4 is a diagram schematically illustrating the optical device 40 foroptically coupling an optical waveguide and an optical fiber in anotherembodiment of the present invention. FIG. 4 shows only a cross-sectionalside view of the optical device 40.

In this optical device 40, an oxide layer 12 is provided on a siliconsubstrate 11, and a silicon optical waveguide 13 is formed on the oxidelayer 12. However, in the optical device 40, the conversion meansprovided on one end of the silicon optical waveguide 13 to convert thelight propagating through the silicon optical waveguide 13 to parallellight and to output the parallel light is not a grating means 21 asshown in FIG. 2 and FIG. 3. Instead, an extended portion 41 of thesilicon optical waveguide 13 is provided on the oxide layer 12, and areflective plate 42 is provided on one end of the extended portion 41which forms a 45-degree incline to reflect the propagation light. A lens43 is also provided on the silicon substrate 11 on the side opposite theoxide layer 12, which has a focal point at the point where thepropagation light is reflected by the reflective plate 42. This lens 43converts the light reflected by the reflective plate 42 into parallellight.

The lens 43 has a convex lens surface 44 on the side opposite thesilicon substrate 11 on which it is arranged. The light reflected by thereflective plate 42 widens inside the lens 43 and reaches the convexlens surface 44. The light is then outputted from the convex lenssurface 44 as parallel light.

As in the optical device 20 of FIG. 2, the parallel light outputted fromthe convex lens surface 44 of the lens 43 strikes the convex lenssurface 23 of a lens 22 provided as a lens means for focusing theparallel light on the core 15 of the optical fiber 16. As in the case ofoptical device 20, optical device 40 does not require direct alignmentby the lens 22 of the optical fiber with a high degree of precision.Also, because the convex lens surface 44 of the lens 43 can bemanufactured with a high degree of precision using a molding process,optical device 40 achieves high optical coupling efficiency.

FIG. 2 and FIG. 4 show optical coupling for communication in which lighttravels from the silicon optical waveguide 13 to the optical fiber 16.However, optical devices 20 and 40 can also be used to perform opticalcoupling with a high degree of optical coupling efficiency forcommunication in which light travels from the optical fiber 16 to thesilicon optical waveguide 13.

The present invention was explained above using an embodiment, but thetechnical scope of the present invention is not limited in any way bythis embodiment. It should be clear to a person of skill in the art thatvarious modifications and improvements can be made without departingfrom the spirit and scope of the present invention.

What is claimed is:
 1. An optical device comprising: a conversion meansfor converting propagation light propagating through an opticalwaveguide into parallel light and for outputting the parallel light; anda first lens means for focusing the parallel light outputted from theconversion means on a core of an optical fiber.
 2. The optical deviceaccording to claim 1, wherein the conversion means includes a gratingmeans to bend the propagation light at a right angle to convert thepropagation light to parallel light.
 3. The optical device according toclaim 2, wherein the grating means is a reflective surface provided witha plurality of V-shaped grooves arranged in parallel, in which thesurface on one side of each V-shaped groove forms a 45-degree incline.4. The optical device according to claim 1, wherein the conversion meanscomprises: a reflecting means forming a 45-degree tilted surface forreflecting the propagation light; and a second lens means, having afocal point at a point on which the propagation light is reflected bythe reflecting means, that converts the propagation light reflected bythe reflecting means into parallel light.
 5. The optical deviceaccording to claim 1, wherein the parallel light strikes a convex lenssurface of the first lens means, and wherein opposite the convex lenssurface of the first lens means a recess is formed for accommodating theoptical fiber so the parallel light is focused on the core of theoptical fiber.
 6. The optical device according to claim 1, wherein theoptical waveguide is a silicon thin-film waveguide.
 7. A method formanufacturing an optical device comprising: converting propagation lightpropagating through an optical waveguide into parallel light; outputtingthe parallel light; and focusing, using a first lens, the parallel lighton a core of an optical fiber.
 8. The method for manufacturing anoptical device according to claim 7, wherein converting the propagationlight includes bending the propagation light at a right angle to convertthe propagation light to parallel light.
 9. The method for manufacturingan optical device according to claim 8, wherein bending the propagationlight is carried out using a reflective surface with a plurality ofV-shaped grooves arranged in parallel, in which the surface on one sideof each V-shaped groove forms a 45-degree incline.
 10. The method formanufacturing an optical device according to claim 7, wherein convertingthe propagation light further comprises: forming a 45-degree tiltedsurface on a reflective surface for reflecting the propagation light;and using a second lens having a focal point at a point on which thepropagation light is reflected by the reflective surface to convert thepropagation light reflected into parallel light.
 11. The method formanufacturing an optical device according to claim 7, wherein theparallel light strikes a convex lens surface of the first lens, andwherein opposite the convex lens surface of the first lens a recess isformed for accommodating the optical fiber so the parallel light isfocused on the core of the optical fiber.
 12. The method formanufacturing an optical device according to claim 7, wherein theoptical waveguide is a silicon thin-film waveguide.